(1) Field of the Invention
This invention is directed to systems and methods for reducing groundwater contamination by volatile organic compounds where the groundwater is in close proximity to a methaneogenic source commingled with volatile organic compounds (VOCs)—such as landfills—by injecting a gas, such as air, into the unsaturated or vadose zone of soils or bedrock located outside of the methaneogenic source in order to create a positive-pressure curtain to inhibit landfill gas migration and/or to transform the subsurface environment from anaerobic to aerobic conditions in the saturated zone to facilitate the remediation of volatile organic compounds that are capable of being treated under aerobic conditions.
(2) Description of the Art
Modern landfills are designed and constructed to contain solid and liquid wastes and minimize the potential for gases (such as landfill gas) to be emitted or migrate from the containment facility. However landfill gas (which is generally composed of methane, carbon dioxide, and trace organic compounds) is a common source of localized impacts to groundwater. A few of these organic compounds (such as PCE and TCE) degrade rapidly under anaerobic conditions. Other compounds, however, (such as vinyl chloride) are relatively persistent under anaerobic conditions but degrade rapidly under aerobic conditions.
Currently, VOC migration into groundwater adjacent to landfills is minimized—to the extent that it is a problem—by either (1) mitigating migration at the source with enhanced leachate or landfill gas extraction, (2) treating VOC contaminated groundwater to remove VOCs; or (3) by applying oxidizing agents or other remediation chemicals into the landfill to enhance aerobic bioremediation and reduce the anthropogenic VOCs into a more natural (and less of a threat to human receptor) state. The cost and complexity of these types of remediation can be high and the manpower required to operate these processes is also quite high.
There is a need, therefore, to provide technologies to address impacted groundwater from contaminants that can be addressed under both anaerobic and anaerobic conditions. Moreover, there is a need for simpler, less time-consuming and less labor-intensive methods for inhibiting the migration of volatile organic compounds from methaneogenic sources such as landfills into surrounding groundwater. Value is provided to the industry if these technologies can address the impact as a part of enhancements to the routine operation and maintenance (O&M) of landfills and other methaneogenic sources rather than as a post-impacted groundwater remediation solution.